Drafting machine brake



Oct. 12? 1943. F, Q EUBANKS DRAFTING MACHINE `BRAKE 2 Sheets-Sheet l Filed Nov. 6, 1959 Snvcntor: F/ ov G. faena/rs. 7a u MMM.

Oct. l2, 1943. F. G. EUBANKs DRAFTING MACHINE BRAKE Filed Nov. 6, 1939 2 Sheets-Sheet 2 Ill/lll Gttorneg Patented oct. 12, l1943 DRAFTING MACHINE BRAKE Floyd G. Eubanks, Pasadena, Calif., assigner, by direct and mesne assignments, of thirty-one and one-half per cent to Francis E. Vaughan, Pasadena; five per cent to Robert M. McManigal, Compton; six per cent to Edward Floyd Eubanks, six per cent to Philip Robert Eubanks, six per cent to Patricia Rose Eubanks, eight per cent to Philip Alfred Vaughan, and

eight per cent to Edward Urner Vaughan, all

of Pasadena, Calif.

Application November 6, 1939, Serial No. 303,054

lly Claims.

My invention relates to a drafting machine comprising a fixed member clamped to a drawing board, an arm pivoted at one end to the fixed member, a second arm pivoted at one end tothe moving end of the first arm through a joint referred to as the elbow, and a drafting head carried at the free end of the second arm and movable over the drawing board. The drafting head includes a protractor and a protractor arm provided with a Vernier or witness point and with means for holding one or more rulers or straight edges which can be rotated about the protractor. As the drafting head is moved over the drawing board, orientation of the protractor arm is held constant by some combination of pulleys and bands.

When such a drafting machine is used on an inclined board the drafting head tends to slide down olf of the board and the object of my invention is to provide a means for retarding this movement of the drafting machine due to the inclination of the board.

The object of my invention is to provide a braking device at the elbow by which frictional resistance between the elbow pulley, the upper elbow bracket, and the lower elbow bracket is produced.

Another object of my invention is to provide means for controlling the frictional resistance between the elbow pulley, the upper elbow bracket, and the lower elbow bracket produced by the braking device at the elbow.

My invention has other objects, advantages, and features, some of which, with the foregoing, will be apparent from the following description and accompanying drawings of what is now considered to be a preferred embodiment of the nvention. it should be understood, however, that this particular embodiment of the invention is chosen for the purpose of exempliiication, and I do not limit myself to the form shown, since the invention, as set forth in the claims, may be embodied in a large plurality of forms.

Referring to the drawings:

Figure 1 is a plan view of a drafting machine of the pulley and band type embodying my invention.

Figure 2 is a plan View of the elbow of the machine showing certain features of my invention.

Figure 3 is a sectional View taken along the line 3 3 in Figure 2 and showing certain details of construction of the machine.

Figure 4 is a plan view taken along the line ll--ll in Figure 3.

Figure 5 is a plan view taken along the line 5 5 in Figure 3. n

Referring to said drawings, the numeral -II indicates any conventional clamp for holding'the drafting machine to a drawing board I2. The clamp I I carries a pivot shaft rising perpendicularly to the board, to which is rigidly afxedA a single groove `pulley (not shown) which is engaged by the band I3. An arm I4 is'pvoted 'to the shaft by a suspension head I5 in suchY a mannerthat it can be rotated about said shaft. Attached to the other end of the arm M is Athe upper elbow bracket It. The lower elbowbracket I'I is attached to the adjacent end` of the arml I8. The brackets Iiand` Il 'carry at i9 the axis `of articulation between the arms It and I8. Between the brackets I6 and Il, and mounted on the axis of articulation at I9, is a two groove pulley 2d referred to as the elbow pulley. The band I3 engages the upper `groove of this pulle and a band 2i engages the lower groove. i

The other kend of the armfIS carries a pulley housing 22 within which is mounted a one groove pulley `(not shown) engaging the band 2|. To this pulley are attached a protractor 23, a protractor'arm 2li carrying the rulers 25 and 26 which can berotated about the protractor, and other parts designed to facilitate the work of a draftsman.

AS shown in Figure 3, the elbow pulley 20 is mounted on a tubular pulley shaft 3l. On this shaft and above the pulley is the innerk race 32 of a ball bearing. The outer race 33 is pressed into the upper elbow bracket I5. There is ay similar ball bearing on the shaft SI and below the pulley Z. 'Ihe outer race of this latter bearing is pressed into the lower elbow bracket 'I`I. Nuts 34 and 35, screwed upon the upper and lower ends respectively of the pulley shaft 3 I, hold together upon this shaft the inner race 32 of the upper ball bearing, the bracket pulley 20 and the inner race of the lower ball bearing.

YA brake shaft 35 passes through the pulley shaft SI. A metal plate 3l is firmly affixed to the lower end of the brake shaft. Between the plate 3l and the lower elbow bracket Il vthere is a friction plate 38 which may be formed of leather, cork, Bakelite or other suitable'material. A pin 39 is driven through the shaft 36. The ends of this pin project slightly on either side of the shaft 3S and rest in a slot cut across the lower end of the pulley shaft 3l. The shaft 36 carrying theplate 3l can be moved slightly vertically with respect to the shaft 3|, but vmust rotate with it, and therefore with the elbowpulside of the hole through the plate 40 and its hub 4 I. The plate 40 can be moved slightly vertically with respect to the shaft 36 but must rotate with it, and therefore with the plate 37, the pulleyr shaft 3i and the elbow pulley 20. Tightening the thumb nut 44 on the upper end of the brake shaft 36 tends to bring the plates 31 and 4I! t0- gether squeezing the friction plates 38 and 42 against the lower and upper elbow brackets I1 and I6 respectively. This applies and increases frictional resistance to movements of the elbow brackets I6 and II with respect to each other and with respect to the elbow pulley 2U. By loosening the thumb nut 44 the friction can be decreased.

When the drafting machine is in use on a horizontal drawing board there is no need for the braking device and it can be rendered inoperative by loosening the thumb nut 44. When the machine is on an inclined board the drafting head tends to slide down and off of the board. This can be prevented by tightening the nut 44 and increasing the braking action between the brackets I6 and I1 and the elbow pulley 20. In practice the braking action should be sufiicient to hold the drafting head at various positions on the board Without requiring undue effort to move it over the board.

The principal advantages of the braking device of my invention are simplicity in construction and maintenance, the application and adjustment of frictional resistance between three members with but a single nut, equality of frictional resistance produced between the three members concerned, the two elbow brackets I6 and I1 and the elbow pulley 21], and the even distribution of the wear on the friction plates 38 and 42, which wear is automatically taken care of in the actual operation of the device.

From the foregoing description taken in connection with the accompanying drawings, other advantages, and the operation of the drafting machine elbow brake of `my invention will be readily understood by those skilled in the art to which the invention appertains. While I have described the principle of operation together with the form of my invention which I now consider to be the best embodiment thereof, I desire to have it understood that the device shown is merely illustrative and that the invention is not to be limited to the details disclosed herein, but to be accorded the full scope of the appended claims.

I claim:

l. In a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a low elbow bracket spaced from said upper elbow bracket, an elbow pulley positioned between said elbow brackets and rotatable with respect to said brackets, a shaft extending through said elbow pulley and connected to rotate with said elbow pulley, an upper shaft plate mounted above said upper elbow bracket, a lower shaft plate mounted below Said lower elbow bracket, said shaft plates being secured at opposite ends of said shaft to rotate therewith, a friction plate to produce braking action between said upper shaft plate and said upper elbow bracket, a second friction plate to produce braking action between said lower shaft plate and said lower elbow bracket, and means to adjust said shaft plates with respect to said elbow brackets to control the braking action imposed by said friction plates.

2. In a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a lower elbow bracket spaced from said upper elbow bracket, an elbow pulley positioned between said elbow brackets and rotatable with respect to said brackets, a shaft extending through said elbow pulley and connected to rotate with said elbow pulley, an upper shaft plate mounted above said upper elbow bracket, a lower shaft plate mounted below said lower elbow bracket, said shaft plates being connected to rotate with said shaft, a friction plate to produce braking action between said upper shaft plate and said upper elbow bracket, a second friction plate to produce braking action between said lower shaft plate and said lower elbow bracket, a second shaft within said rst mentioned shaft, said second shaft being connected to said lower shaft plate and threaded at the upper end, and a member threadedly engaging said second shaft whereby rotation of said member with respect to said second shaft controls the pressure of the shaft plates with respect to the friction plates.

3. l'n a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a lower elbow bracket, an elbow pulley rotatable with respect to said elbow brackets and positioned therebetween, an opening through said pulley, a hollow shaft extending through said opening, means interconnecting said hollow shaft and pulley to cause the same to rotate together, a friction brake member operatively positioned abc-ve said upper elbow bracket to produce braking action between said upper elbow bracket and said pulley, a second friction brake member operatively positioned below said lower elbow bracket to produce braking action between said lower elbow bracket and said pulley, a second shaft within said hollow shaft connecting said brake members, said second shaft being threaded at one end and a member threadedly engaging the threads of said second shaft whereby rotation of said member with respect to said second shaft controls the braking action created by said brake members.

4. In a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a lower elbow bracket spaced from said upper elbow bracket, an elbow pulley positioned between and rotatable with respect to said elbow brackets, a hollow shaft extending through said pulley, said pulley being secured against rotation on said hollow shaft, a disk mounted above said upper elbow bracket, a second disk mounted below said lower elbow bracket, said disks being connected to rotate with said hollow shaft and pulley, a non-inetallic friction brake member between said upper disk and said upper elbow bracket, a second non-metallic friction brake member between said lower disk and said lower elbow bracket, a second shaft within said hollow shaft, said second shaft being secured at its lower end to said second disk and being threaded at its upper end, and a member threadedly engaging said second shaft whereby rotation of said member with respect to said second shaft controls the degree of braking action imposed by said non-metallic brake members.

5. In a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a lo-wer elbow bracket, an elbow pulley positioned between said brackets and rotatable with respect thereto, an opening through said pulley, a shaft extending through said opening, means interconnecting said pulley and said shaft to cause the same to rotate together, a friction brake member mounted on said shaft to rotate therewith and positioned to produce braking action between said upper elbow bracket and said pulley, a second friction brake member mounted on said shaft to rotate therewith and positioned to produce braking action between said lower elbow bracket and said pulley, and means on said shaft for adjusting the braking action created by said brake members. y

6. In a drafting machine of the band and pulley type, the combination of an upper elbow bracket, a lower elbow bracket spaced from said upper elbow bracket, an elbow pulley positioned between and rotatable with respect to said elbow brackets, a brake shaft extending through said brackets and pulley, said shaft being rotatable with said pulley, a disk mounted above said upper elbow bracket, a second disk mounted below said lower elbow bracket, said disks being secured to oppositel ends of said brake shaft to rotate therewith, a non-metallic friction brake member between said upper disk and said upper elbow bracket, a second non-metallic friction brake member between saidA lower disk and said lower elbow bracket, and means to adjust said disks with respect to said elbow brackets to control the braking action imposed by said non-metallic brake members.

7. In a drafting machine including a parallel motion mechanism of the endless band and jointed strut type, an elbow joint comprising: an elbow pulley disposed between adjacent ends of a pair of said struts; a, pivot sleeve extended axially through said pulley and immovably secured thereto; means mounting said adjacent ends of said struts upon opposite ends of said sleeve for independent pivotal movement relative to said pulley; a brake plate carried by each end of said sleeve; means mounting said plates on said sleeve for non-rotating sliding movement into and out of engagement with an adjacent strut; shaft means secured vat one end to one of said platesextended through said sleeve and through the other of said plates; and control means carried by the other end of said shaft engageable with said other plate for simultaneously moving both of said plates into engagement with said struts.

8. In combination with a drafting machine including an elbow pulley and a pair of struts disposed on opposite sides thereof and secured thereto for pivotal movement about the axis of said pulley; a braking device comprising a means for frictionally inter-engaging both of said struts with said pulley, whereby pivotal movement of each of said struts relative to said pulley is frictionally resisted.

9. In combination with a drafting machine including an elbowpulley and a pair of struts disposed on opposite sides thereof and secured thereto for pivotal movement about the axis of said pulley, means defining a pail of braking surfaces fixed against rotation relative to said pulley, and means on each of said struts defining another braking surface fixed against rotation relative to said strut, said other surfaces frictionally engaging said first-named braking surfaces.

10. In combination with a drafting machine including an elbow pulley assembly and a pair of struts disposed on opposite sides thereof and secured thereto for pivotal movement about the axis of said pulley assembly; a braking device for each of said struts comprising a means for fric tionally inter-engaging such struts with said pulley assembly; and a single control means connected to both of said braking devices for simultaneously regulating the degree of frictional inter-engagement between said pulley assembly and each of said struts.

11. In combination with a drafting machine including an elbow pulley and a pair of struts pivotally attached to said pulley, a brake member for each of said struts carried by saidpulley, and friction material interposed between each of said brake members and the associated one of said struts for frictionally resisting relative pivotal movement between said struts.

FLOYD G. EUBANKS. 

